Purple ecchymosis on both sides of the buttocks is considered to be related to local trauma, frostbite, allergic purpura and other factors, and needs to be analyzed according to the symptoms. 1. Local trauma: for some patients, it may be due to the factor of violent blows, thus causing the capillaries under the buttocks to rupture and bleed, accumulating in the subcutaneous, so the formation of purple ecchymosis on both sides of the buttocks. 2. Frostbite: If it occurs in the cold winter, it can not be ruled out and the patient is in the low-temperature environment for a long time, which may cause frostbite in the skin area, so the formation of purple ecchymosis on both sides of the buttocks. 3. Anaphylactic purpura: this belongs to the allergic inflammation of the relevant parts of the whole body acupuncture points, the patient may be infected with immune disorders or hereditary factors, resulting in the emergence of anaphylactic purpura, some of the patients will also appear on both sides of the buttocks purple ecchymosis phenomenon. Purple ecchymosis on both sides of the buttocks may also have other causes, so you need to cooperate with the doctor to improve the examination and determine the cause before handling and treatment.